Neither NASA nor the Russian space agency can account for how sea plankton ended up on the outer hull of the ISS. One far-fetched explanation says that atmospheric currents might be lifting the lifeforms up from the ocean all the way to the ISS — which is 205 miles in the sky.

The lifeforms were found when cosmonauts on a clean-up mission analyzed engine gunk that had dirtied the surface of the ISS.